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Bureau of Workers’ CompPA Training for Health & Safety

(PATHS)

29 CFR 1910.30329 CFR 1910.30529 CFR 1926.400-449,Subpart KNFPA 70E

ARC FLASH SAFETY

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OSHA Cited Violations: FY 2010

OSHA has long understood the importance of safety in this area and tracks electrical violations

OSHA Most Cited Violations (2010)• Electrical-General Requirements (1910.303): 2,770• Lock-out/Tag-out (1910.147): 3,531

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OSHA Violations FY 2010

1926.400-449, Subpart K

• 404(f)(6) Grounding path 473• 404(b)(1)(i) Ground fault protection 338• 405(g)(2)(iv) Flexible cords-strain

relief 277• 416(e)(1) Worn/frayed cords

or Cables256

• 403(b)(2) Equipment installation and use

241

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OSHA Violations FY 2011

• 1910.147 Lock-out/Tag-out 3,639• 1910.305 Electrical-wiring

Methods 3,584• 1910.303 Electrical-General

Requirements2,863

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Electrical Hazards

• Shock

• Electrocution: 4th leading cause of industrial fatalities

• Fires

• Burns

• Arc Flash

• Arc Blast

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Arc Flash Defined

• Electrical work may cause injury or death• One severe occurrence is the Arc Flash event

“Arc Flash: an electrical discharge that uses the air as a conductor, exploding from a high voltage source to another conductor or ground nearby. The release can be 5,000oF or hotter, melting nearby metals and damaging the electric circuits involved. The brightness, heat and force of the arc flash can cause damage to the human body.”

Tyler Lacoma, eHow Contributor, http://www.ehow.com/about_5110071_definition-arc-flash.html

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Arc Flash

Hazards resultingfrom arch flash:

• Heat• Shrapnel• Pressure• Sound• Intense light

UV IR

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Arc Flash Hazards

Statistics:*5 to 10 such serious arc flashes a day occur in the United States

Result: 1 to 2 fatalities

Although protective clothing exists, there is no guarantee against such severe energy releases

*Dr. Mary Capelli-Schellpfeffer, “Arc Flash Presentation,” as quoted in eHow.com facts, May 30, 2012

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Causes of Arc Flash

• Overloading/overheating of circuits

• Damaged circuit breakers

• Over-fusing

• Wiring in a non workman -like manner

• Faulty electrical panels

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Causes of Arc Flash

• System overload

• Incorrect wire gauge for system requirements

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Causes of Arc Flash

Faulty panels or overloading panels

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Arc Blast

• Accompanies the flash

• Intense radiant heat released

• Nearby surfaces (persons and objects) absorb and are instantly heated to vaporizing temperatures

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Arc Blast Hazards

Serious situations!!

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Electrical System Susceptibility

System Hazard

Less then 120V Arc flash highly improbable

480V electrical Sufficient capacity to causeservices

Above 600V Medium-voltage with higherenergy/potential for an arcflash event

http://en.wikipedia.org/wiki/Arc_flash

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Arc Flash Energy Released

Per Wikipedia

Example: single phase-to-phase fault on 480V system with 20,000 amps of fault current

Resulting power is 9.6 MW

If fault lasts 10 cycles at 60Hz, resulting energy would be 1.6 megajoules

Comparison: TNT releases 2,175 J/g or more when detonated. This fault is equal to 380 grams (about 0.8 pounds) of TNT !!!

http://en.wikipedia.org/wiki/Arc_flash

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Possible “Traps”

Beware of a “profusion of electrical confusion”

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Current/Reaction Chart

Current ReactionBelow 1 milliampere Generally not perceptible.1 milliampere Faint tingle.5 milliampere Slight shock. Not painful-disturbing. Average

person can let go. Strong involuntary reactions can lead to other injuries.

6-25 milliamperes Painful shock. Loss of muscular control. (women)9-30 milliamperes Freezing current (“let-go” range). Person can not

let go but can be thrown from the current if extensor muscles are stimulated.

50-150 milliamperes Extreme pain, respiratory arrest, severe muscular contractions. Death is possible

1,000-4,300 Rhythmic pumping action of heart ceases. Muscular milliamperes contraction and nerve damage occur; death likely.10,000 milliamperes Cardiac arrest, severe burns; death probable.

OSHA Training Institute, “Construction Focus Four: Electrocution Hazards,” April, 2011

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Need for an Arc Flash Study

• Numerous inherent dangers when working around electrical systems

• Safety from arc flash should include an Arc Flash Study

• Done prior to conducting work on hazardous locations

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Arc Flash Study

Study components per IEEE 1584:Data Collection (steps 1 & 2)System diagramsModes of operation scenariosAnalysis (steps 3-7)Determination of bolted fault currentsProtective devices recommendedDocument system voltages & classes of equipmentDetermine working distance from arc flash source

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Arc Flash Study

Arc Flash Hazard Analysis (Steps 8 & 9)

Incident energy determination(Energy needed for an arc flash to cause

second-degree burns)

Flash protection boundaries (Distance where the second-degree burns

are caused, or where the incident energy is 1.2 calories per centimeter squared or 1.2 cal/cm2)

Both may be calculated using NFPA or IEEE equationsDiane Bonder, eHow Contributor

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Aids to Safe Operations

• NFPA 70E-2004 Standard for Electrical Safety Requirements for Employee Workplaces

• IEEE 1584 Guide for Arc Flash Hazard Calculations

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Arc Flash Hazard Analysis

Results aid in determining:

Proper PPE, distance-dependent from possible threat:

- Shirts- Pants- Underwear- Goggles- Gloves

- Hard hats- Shields, face and neck- Heating protection- Shoes

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Safe Distance Calculations

Used to determine safe distances and PPE

Variables taken into account:

• Voltage

• Working distance

• Clearing time

• Grounding

• Gap between conductors

• Bolted fault current

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Arc Flash Boundaries

“Distance from an arc flash within which an

unprotected person has a 50% chance of

receiving a second degree burn”

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Flash Protection Boundary

Arc flash hazard is based on:

• Fault current• Arcing time• Distance

Preplanning your facility will enhance the safety of your staff

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PPE Based on Incident Energy Preplan

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PPE by Hazard Risk Category

Findings compared to table which indicates arc thermal performance of clothing

Dangers above a 4 is prohibited

“No Safe PPE Exists Energized Work Prohibited”

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Definitions

• Voltage (E): electromotive force (emf) that forces electrons to flow through a circuit measured in Volts (V)

• Current (I): the number of electrons that flow past a point in a circuit in one second measured in Amperes or Amps (A)

• Resistance (R): the opposition to current flow in a circuit that contains only resistance and is measured in ohms

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• Relationship between E, I, R• “One volt of electromotive force will force one ampere of current to flow through one ohm of resistance”

E

I R

By knowing 2 of these variables, the other can be calculated!

Ohm’s Law

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Power Formula

• Power: the rate at which work is done and is measured in Watts (W) (E x I)=Watts

• So Power is equal to P= E x I

• Power can be measured in the thousands of watts per

hour and reads as KWH or kilowatthours

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Horsepower and Watts

• Horsepower is the unit of measure for mechanical energy

• 746 Watts = 1 Horsepower

(hp) or P = E x I • Flow of Amps= E/R

• Additional information

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Qualified Person

• Qualified Person: One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved

• OSHA defines these as specially trained to work on live electrical equipment • Unqualified Person: per 1910.332(b)(2) must still be trained in safe electrical practices for their support jobs (painters, cleaners as examples)

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Types of Damage

Fully understand the hazards related to these activities

If possible, review case histories of your industry to devise safe operations

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Caution!!

Abide by distances determined by NFPA or IEEE

NO SHORT CUTS!!!

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Signage

Ensure signage fits hazard and conforms to regulatory requirements

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Hazard Preplan

• Use checklists to preplan equipment needs when performing service or

maintenance

• Label systems for future maintenance and arc flash studies

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Safety Precautions: PPE

• PPE should fit the requirements of the job

• Specific level of PPE is required

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PPE

Tests for arc rating of PPEFound in ASTM F1506 “Standard Performance Specifications for Flame Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards”

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Match PPE to Task

Level 2 Protective Coverall

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Match PPE to Task

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Match PPE to Task

Prepare for the possible!

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Tools

• Support equipment rated for the task

• Tools properly insulated

• Correct support equipment for the job

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Safety

Robotic removal or disengagement devices can do much to maximize personnel safety

Also:• Draw-out circuit

breakers on a life bus• Remote racking

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Safe Work Practices

Lock-out/Tag-out:

Make sure you’re wearing the proper PPE for this job also

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Avoiding Arc Flash

Assign qualified person• Conduct system analysis to determine arc flash hazard• When working, secure all power and enact Lock- out/Tag-out• Proper tools and PPE rated for the job• Assign electrical safety program manager familiar with codes• Properly maintain system and components• Apply warning labels

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Some Questions OSHA will Ask

From EHSToday, March 13, 2008 (and still timely), Kenneth Cybart:

OSHA’s goal: for employers to identify all electrical hazards, potential and actual

Analyze workplace for shock and arc flash hazards, set safe protection boundaries and define required PPE

Circuit or equipment description at job location? Written description, drawing

Detailed job description of work?

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Some Questions OSHA will Ask

Can the fact that the equipment cannot be de-energized or job be deferred be justified?

1910.333(a)(1) Live parts must be de-energized before employee works on/near themLess than 50 volts to ground need not be de-energized if there will be no increased exposure to electrical burns or to explosion due to electric arcs

However, never work on live circuits unless absolutely necessary

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Some Questions OSHA will Ask

Live circuit work necessary?

OSHA 1910.33(a)(2): Safety-related work practices required

NFPA 70E Article 110.8(B)(1): Electrical Hazard Analysis required before work performed on live equipment operating at 50 volts and higher

Other questions to ask:- Safe work procedures?Detailed work procedure established? Will it be

used?Job briefing checklist performed?

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Some Questions OSHA will Ask

Was job briefing given to those doing the job?

Proper management approval obtained?

NFPA 70E annexes to assist your program:

Annex Topic

E Electrical Safety Programs F Hazard Risk Evaluation Procedures I Job Briefing Checklists J Energized Work Permits

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Some Questions OSHA will Ask

Electrical safety analyses performed?

Arc flash hazard analysis performed?

Flash protection boundaries established?

Other potential electrical hazards identified?

Proper insulated tools and equipment used?

Necessary PPE determined?Insulated blankets/sheeting used to cover all liveparts?

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Some Questions OSHA will Ask

OSHA: Every employer shall furnish a place of employment free from recognized hazards…causing or likely to cause death or serious physical harm… NFPA 70E: Employers to conduct an electrical hazard assessment to include a hazard analysis for shock and arc flash before performing work on live equipment operating at 50 volts and higher

Review the following when creating your program: OSHA 1910.132 and 1910.333(a)(1)(i) as well as 1910.269(a)(2)(iii)

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Summary

• Appreciate the severe consequences which are possible when working with electrical systems

• Fully plan the job; know and enact safeguards

• Match the required PPE and equipment to the task

• Consider possible emergency response needs for

yourself and your team and include in your plan

• Conduct the job safely

• Restore safely

• GET HOME SAFELY!!!

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Bibliography

http://en.wikipedia.org/wiki/Arc_flash

Tyler Lacoma, eHow Contributor, http://www.ehow.com/about_5110071_definition-arc-flash.html

Dr. Mary Capelli-Schellpfeffer, “Arc Flash Presentation,” as quoted in eHow.com facts, May 30, 2012

Diane Bonder, eHow Contributor

OSHA Training Institute, “Construction Focus Four: Electrocution Hazards,” April, 2011

http://ehstoday.com/construction/ehs_imp_79112

Questions

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